Narwhals: Let’s Dive Deeper.

Narwhals (Monodon Monoceros) are a species of whale that can be found in the arctic waters of Greenland, Russia and Canada. They are odontocetes (toothed whales) however they are unique as they lack teeth in their mouth and instead have a single spiral tusk. They are commonly known as the unicorn of the sea, due to their large tusk which extends from their upper jaw which can reach lengths of 2-3m. The tusk is mostly present in males, however females can rarely develop one, however it is much shorter than those present on males. Little is known about narwhals, and there is much speculation regarding the primary function of their tusk. In recent years the narwhal has moved from “near threatened” to “least concern” under the IUCN classification.

Description

Male narwhals can reach up to 5m in length and weigh a maximum of 1800kg, whereas the females only reach 4m and 1000kg. In order to survive the extreme cold of the arctic, narwhals have developed an extremely thick layer of blubber which accounts for up to a third of their total weight. This blubber is extremely valuable to the Inuit people as it is frequently consumed for its rich vitamin content.

Narwhals have a black and white skin pattern as well as a pale underside. This colouration helps with camouflage, to reduce the risk of being predated upon. This colouration has been said to look like a drowned sailor, where they also earned the Old Norse name of “corpse whale”

Diet

They are a carnivorous whale and while no direct observations of their feeding habits have been conducted it would appear they have a rather specialised diet. This has been concluded by many years of examinations of narwhal stomachs. The primary food consists of Greenland Halibut (Reinhardtius hippoglossoides) and Arctic Cod (Arctogadus glacialis) the majority of this feeding occurs during the winter period where feeding is much more intensive, throughout the summer months there is very little feeding.

Tusk

As mentioned previously, the usage of the tusk isn’t fully understood. While it looks like it should have a significant role in the survival of narwhals this is not the case, as females both live longer and only have tusks in extremely rare cases. A few of the theorised usages of the horn are as follows:

Probing. Some people have suggested that the horn is used to probe the sediment as a method to flush out prey, or alternatively to spear their prey. Drone footage has observed narwhals using their tusk to strike their prey, rendering it immobile, this makes feeding much easier for the narwhal.

Another suggestion is that the tusk is used to bore through ice to create an area where the narwhals can surface should they become trapped under the ice, however this theory is slightly flawed as a large proportion of narwhal deaths occur due to suffocation due to being unable to surface.

The most likely theory however is that as narwhals are largely social animals, travelling in pods of anywhere from 10 to 100 individuals, the tusk is used in dominance displays to establish the hierarchy in the pod. This has been observed in the summer from Northern Canada, where males interlock tusks while producing a sad whistle.

Deep divers

Narwhals are extremely capable divers, in the summer they frequently dive down to around 300m, but spend most of their time near the surface. During winter however, once they’ve reached their winter grounds, they demonstrate some of the deepest diving by marine mammals. For the 6 months they’re restricted by ice they frequently dive to 800m, between 18 and 25 times per day, they can even reach depths of 1500m. Due to the extreme pressure of the deep water, narwhals have had to adapt to be able to withstand the toll on their bodies.

Myoglobin is a protein that is found in the muscle tissue of nearly all mammals, which allows for the binding of iron and oxygen. It is significant as a higher concentration of myoglobin allows for an organism to hold its breath for a long period of time, which is important in the case of narwhals as they have double the amount of myoglobin than some seal species, and as a result can carry 70 litres of oxygen in their blood, muscles and lungs. The muscles of the narwhal have also been specialised for deep water swimming as they are built for endurance, meaning that the oxygen consumption is lower. All of these features reduce the amount of oxygen that the narwhal uses, allowing them to remain submerged for up to 25 minutes at a time.

Mythology

Though it sounds far-fetched, it is believed that narwhals are one of the origins of the unicorn. This is because fishermen or Vikings would remove the horns of narwhals and sell them to people without properly describing the source, or exaggerating tales of unicorns. These horns were coveted as they were believed to have healing properties.

According to Inuit myth, the narwhal’s tusk was formed when a woman was dragged into the ocean after her son harpooned a narwhal, whilst having the rope tied around her. The legend states that as the woman had her hair tied in a knot this eventually morphed into the iconic narwhal horn.

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Extreme marine habitats is a site dedicated to those habitats that are simply extreme! Written by students, we aim to provide detailed and insightful information on a variety of marine science subjects.